VVER design

The VVER-440 reactors are always built in modules of two units which are housed in one single reactor building. Each reactor has six loops, isolation valves in each loop, and horizontal steam generators arranged around the reactor pressure vessel each reactor supplies two 220 MW turbines. The reactor pressure vessel has 

Each of the steam generators of the WER-440 plants is equipped with 5536 heating tubes, which gives a total heat exchange surface of 2510 m. The tubes are fabricated of the stainless steel Crl8N9T, the shell and the tube sheet of a low-alloy carbon steel. 

The reactor core contains 349 hexagonal fuel assemblies, each of them consisting of 129 fuel rods with a diameter of 9.1 mm and a length of 3.21 m the fuel rods are kept in position by 15 honeycomb-type spacer grids which are fixed on a central channel. Seventy-three of the fuel assemblies contain movable control assemblies with boron steel as an effective material in the V213 fuel assemblies, six of the fuel rods are replaced by fixed burnable poison rods. 

The plants at Loviisa, Finland, though they are also of the V230 type, are equipped with a concrete containment surrounding the primary system. In addition, they are provided with an ice condenser pressure suppression system. 

The newer VVER-440 model 213 differs from the 230 in that it has an emergency core cooling system with limited capacity and a bubbler/condenser tower which is connected with the accident localization compartments of each unit to mitigate the effects of severe accidents. This tower has a rectangular cross section and contains 12 levels of suppression pool trays (in total about 1960 trays). The tower also houses four large receiver volumes referred to as gas holders or air traps. 

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VVER (design AES -2006 or VVER-1200 with 1200MWd) GIDROPRESS, Russia (4 under construction in Russia and several more planned to be built in various countries, including Belarus, Finland, Turkey, Vietnam, etc.)... 

The important features of the PWR core are shown in Figure 19.12 and described in 19.13.1. The design with a pressure vessel without facilities for fuel handling imder pressure necessitates a yearly shutdown for fuel rq>lacement. However, this is not considered a great inconv ence as a PWR anyhow has to be shutdown on a regular basis for safety inspection of pipes, welds, etc, and for routine maintenance. The need to shut down the reactor and open the pressure vessel in order to replace fuel also makes the PWR (as well as the VVER) resistent to concealed nuclear proliferation. 

It may be noted that the RBMK reactor design was chosen by the USSR (despite warnings from the Soviet Academy of Sciences) because it was better suited to available production facilities than the VVER types (which required the manufacture of large pressure vessels). The rapid introduction of RBMK reactors in the USSR made previously used energy resources (oil and gas) available for export to the West, giving a very needed hard currency income. 

An overview of the cooperative program to improve the safety of Soviet-designed nuclear power plants is provided in Section 2. The applicability of that work to safety improvements that would be desirable for VVER-1000s under a MOX fiiels program is outlined in Section 3. A summaiy and some observations on plutonium disposition are provided in Section 4. 

An overview of the cooperative effort between the U.S. and nine host countries to improve the safety of Soviet-designed nuclear power plants was provided. Elements of the cooperative effort that apply to ensuring that MOX fuel can be burned safely in Russian VVER-1000 nuclear power plants were identified. 

Both programs also developed concepts for pilot plants to fabricate fuel for these reactors. They were designed for capacities of approx. 1 to 1.3 t Pu/year, representing the consumption of four VVER-1000s and one BN-600 reactor. 

At the moment, there are no transport packages in Russia that are suitable for the transportation of fuel elements and fuel bundles of reactor VVER-1000 with fresh mixed fuel. VNIPIET has performed design studies for such packages and appropriate auxiliaries. The work was conducted in two directions ... 

According to a number of experts, in particular from the former USSR, the attitude of the industry towards safety also changed in Eastern Europe after the TMI accident already in early 1980s, Russian designers of VVER reactors proposed a number of measures for safety improvements. 

In some plant (e.g. some VVERs), this phenomenon is prevented by design since the ECCS injection point is located in the loop seal of the cold legs, where the unborated water would accumulate upon actuation of ECCS, the boron concentration in the slug would be rapidly increased, thus preventing any recriticality danger. 

Kazakhstan has a nuclear scientific-industrial complex which was set up as a part of a nuclear infrastructure of the former USSR. More than 50% of the uranium resources of the former Soviet Union are in Kazakhstan, with seven uranium mines. Two UO2 plants produced up to 35% of the total uranium in the USSR in 1990. There are extensive facilities for producing UO2 pellets for VVER fuel elements from Russian enriched uranium. Kazakhstan has several research reactors and one operating nuclear power plant, the BN-350 fast reactor, which started operation in 1973 with a design life of 20 years. Work on its lifetime extension has the intention of bringing it into compliance with current safety standards. 1995 and 1996 were devoted to this work. In October 1996. experimental investigation on accident-proofdecay heat removal by natural circulation was carried out. The reactor BN-350 was restarted in February 4, 1997 at a power level of 420 MW(th). 

The core is composed of 109 hexagonal fiiel assemblies (FAs) of 238 mm width across flats with active fuel length of 2.5 m. The core equivalent diameter is 2.7 m. This results in low core power density (36 MW/m ). The fuel element design is based on the well developed technology of VVER-fuel. 

The ATS-150 reactor plant (RP) has been developed on the basis of the AST-500 prototype power units and its construction experience, using thoroughly studied and technically proven design decisions and technologies of the VVERs and the Nuclear Steam Supply System being used for icebreakers, whose reliability has been confirmed by the long-term successful operation. 

Russia has produced two main reactor designs, known as VVERs and RBMKs. The former is a type of LWR, whereas the latter are light water-cooled graphite reactors. These reactors predominately exist in Russia, other countries that were part of the former Soviet Union, and Eastern Europe. Both designs use enriched uranium and therefore require UFg conversion. 

Several suppliers have stated that dual-purpose applications, such as in desalting plants are foreseen (Rolls Royce PWR 300, HRB 100-500 and Atomenergoexport VVER-440). It is not proposed to obtain an optimized design through a back pressure turbine but simply to bleed off high-pressure steam at the high pressure turbine. This is in itself a proven and simple method. 

The VVER-440 PWR, for a 440 MW(e) gross nuclear power station, started from a smaller prototype and was first realized in its present size with the third Novo-Voronezh unit which started operation in 1971. Since then 30 units of this type have been successfully built and operated in the USSR and in other countries several more are under construction. This Novo-Voronezh type has been developed to meet current international safety standards the most recent plant to go on line in the USSR is the Kola nuclear power station (4 units) (Fig. 1). The VVER-440 concept provides several options which can be suited to various conditions ranging from hot deserts or those of the arctic tundra to optimal conditions for a power plant in a moderate climate. The sound and reliable design of the plants is confirmed by the excellent operational records of nuclear power plants of this type. 

Fuel element Fuel pin similar in design to a standard fuel element of the VVER-1000 reactor... 

The adoption of fuel assemblies and structures of proven design based on the technologies of marine propulsion reactors, the VVER-1000, the AST-500, and the KLT-40S reactors ... 

A core with the WER type fuel design with a decreased linear heat rate, compatible with the infrastructure of the existing VVER nuclear fuel cycle ... 

The ABV design was developed using operating experience of VVER type reactors and recent achievements in the field of nuclear power plant safety. The main purpose of the project is the creation of small multi-purpose power sources based on proven marine reactor technologies, providing easy transport to the site, rapid assembly and safe operation. 

The results of calculation optimization of the design scheme of a micro fuel element in application to the VVER operating conditions ... 

The RA-8 critical facility has been designed and constmcted to measure neutronic parameters typical of the CAREM core. It provides a reactor shielding block and a reactor tank that can be adapted to contain custom designed reactor cores. Experiments were performed using fuel rods of the same radial geometry and pitch as in the CAREM-25 fuel element. Components of the neutronic calculation lines were validated with the use of data for VVER type reactors obtained in the experiments at ZR-6 Research Reactor (Central Research Institute for Physics, Academy of Sciences, Hungary) and data for PWR critical experiments. 

VBER-150 combines basic engineering solutions originally developed for nuclear propulsion reactors and for recent designs of NPPs with VVER-1000 reactors, and is capable of meeting all essential safety, reliability and efficiency requirements currently considered for new generation power plants. 

Improved fuel design with reduced thickness of fuel cladding and enlarged diameter of fuel pellet currently developed for VVER reactors will also enable the VBER core lifetime to be extended. This would make it possible to ensure VBER-150 operation without on-site refuelling during the whole period between FPU repairs. 

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